Baseline comorbidities in patients with rheumatoid arthritis who have been prescribed biological therapy: a case control study.

AIM To determine whether rheumatoid arthritis (RA) patients who have been prescribed biological agents exhibit a different comorbidity burden than RA patients who take disease-modifying antirheumatic drugs (DMARDs) alone, and to understand the association between comorbidity and other variables, as well as the association between comorbidity and multimorbidity. METHODS This observational case-control study included 114 RA patients treated with biological agents and a control group comprising 163 sex- and age-matched RA patients treated with DMARDs only. Current and previous data regarding the patients' disease activity, comorbidities, and treatments were collected. The data were analysed using bivariate and multivariate regression models. RESULTS The patients who were prescribed biological agents exhibited poorer disease control, received more DMARDs and steroids, and underwent more total joint arthroplasties compared with the patients in the control group. However, the risk factors for cardiovascular disease and the comorbidity frequency were similar between cases and controls. The most prevalent comorbidities were hypertension, obesity, and respiratory, thyroid, and upper gastrointestinal disorders. The incidence of cardiovascular disease was low, and only 29% of the patients exhibited multimorbidities. A bivariate association of age, late diagnosis, joint replacements and a high score on the health assessment questionnaire score (HAQ) with comorbidity was observed. There were also correlations between the Charlson index and age, joint reconstructive surgery, disease activity (DAS28), and HAQ score. However, when binary logarithmic regression models were applied, only patient age remained significantly associated with comorbidity and multimorbidity [hazard ratio, 1.08; 95% confidence interval, 1.05-1.12; p<0.0005]. CONCLUSION RA patients taking biological drugs have a comorbidity burden equivalent to those treated with DMARDs alone. Age is the main predictive factor of comorbidity in these patients.